U.S. patent number 8,885,550 [Application Number 12/446,689] was granted by the patent office on 2014-11-11 for beacon symbol orthogonalization.
This patent grant is currently assigned to QUALCOMM Incorporated. The grantee listed for this patent is Avneesh Agrawal, Alexei Gorokhov, Aamod Khandekar, Ravi Palanki. Invention is credited to Avneesh Agrawal, Alexei Gorokhov, Aamod Khandekar, Ravi Palanki.
United States Patent |
8,885,550 |
Palanki , et al. |
November 11, 2014 |
Beacon symbol orthogonalization
Abstract
Beacon symbols are sent periodically from the base stations in
an OFDM system. The entire power of the base station, or a large
portion of it is concentrated in these symbols, thus they are very
easily recognized by the mobile stations. The frequencies upon
which these symbols are transmitted and the time at which they are
transmitted communicates information such as the base
station/sector identity and the preferred carrier of the given base
station/sector to the mobile station. In order to avoid collision
between the beacon symbols of different base stations and sectors,
the beacon symbols from different base stations/sectors are
transmitted at different symbols times and on different
subcarriers.
Inventors: |
Palanki; Ravi (San Diego,
CA), Gorokhov; Alexei (San Diego, CA), Khandekar;
Aamod (San Diego, CA), Agrawal; Avneesh (San Diego,
CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Palanki; Ravi
Gorokhov; Alexei
Khandekar; Aamod
Agrawal; Avneesh |
San Diego
San Diego
San Diego
San Diego |
CA
CA
CA
CA |
US
US
US
US |
|
|
Assignee: |
QUALCOMM Incorporated (San
Diego, CA)
|
Family
ID: |
39156388 |
Appl.
No.: |
12/446,689 |
Filed: |
October 26, 2007 |
PCT
Filed: |
October 26, 2007 |
PCT No.: |
PCT/US2007/082751 |
371(c)(1),(2),(4) Date: |
April 22, 2009 |
PCT
Pub. No.: |
WO2008/052204 |
PCT
Pub. Date: |
May 02, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20100046447 A1 |
Feb 25, 2010 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60863122 |
Oct 26, 2006 |
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Current U.S.
Class: |
370/328 |
Current CPC
Class: |
H04W
72/04 (20130101); H04L 27/261 (20130101); H04W
28/00 (20130101) |
Current International
Class: |
H04W
4/00 (20090101) |
Field of
Search: |
;370/328 |
References Cited
[Referenced By]
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Other References
International Search Report--PCT/US2007/082751, International
Search Authority--European Patent Office--Mar. 26, 2008. cited by
applicant .
Vishnevsky V M et al: "Beaconing in Distributed Control Wireless
Pan: Problems and Solutions" Consumer Communications and Networking
Conference, 2006. CCNC 2006. 2006 3rd IEEE Las Vegas, NV, USA Jan.
8-10, 2006, Piscataway, NJ, USA, IEEE, (Jan. 8, 2006), pp. 482-486,
XP010893255. cited by applicant .
Written Opinion--PCT/US07/082751, International Search
Authority--European Patent Office--Mar. 26, 2008. cited by
applicant .
Taiwan Search Report--TW096140452--TIPO--Jun. 2, 2011. cited by
applicant.
|
Primary Examiner: Rinehart; Mark
Assistant Examiner: Khirodhar; Maharishi
Attorney, Agent or Firm: Braden; Stanton
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Patent
application Ser. No. 60/863,122 entitled "ORTHOGONALIZATION OF
BEACONS IN A WIRELESS COMMUNICATION SYSTEM" which was filed Oct.
26, 2006. The entirety of the aforementioned application is herein
incorporated by reference.
Claims
What is claimed is:
1. A method of transmitting beacon symbols in different symbol
periods or time slots of a superframe in an OFDM configuration and
on the same or different subcarriers to mitigate collision with
beacon symbols from other sectors and grow the number of available
independent channels for beacon symbol transmissions as a factor of
the additional available symbol periods, comprising: determining
one or more symbol periods for sending one or more beacon symbols
in different symbol periods of a superframe and on different
subcarriers to reduce or avoid collision with one or more disparate
beacon symbols from a disparate source, the one or more symbol
periods being determined from a subset of symbol periods useable
for transmitting beacon symbols; and growing the number of
available independent channels for beacon symbol transmissions as a
factor of the additional available symbol periods by sending the
one or more beacon symbols in the one or more determined symbol
periods.
2. The method of claim 1, the one or more beacon symbols and the
one or more disparate beacon symbols are sent by one or more base
stations or one or more sectors thereof.
3. The method of claim 1, further comprising: determining one or
more subcarriers in the one or more symbol periods for sending the
one or more beacon symbols; and sending the one or more beacon
symbols on the one or more subcarriers.
4. The method of claim 3, wherein at least one of the one or more
subcarriers is determined for the one or more symbol periods using
a maximum distance separable (MDS) code.
5. The method of claim 3, wherein the one or more beacon symbols
are chosen based at least in part on a identifier of a source of
the one or more beacon symbols.
6. The method of claim 1, further comprising encoding a sector
identifier into a beacon code, the one or more beacon symbols being
at least one symbol of the beacon code.
7. The method of claim 1, wherein the one or more symbol periods
are determined based at least in part on a predetermined network
planning configuration.
8. The method of claim 1, wherein the one or more symbol periods
are determined based at least in part on beacon symbol timing
information received regarding other sectors.
9. The method of claim 8, wherein the beacon symbol timing
information is received by a mobile device.
10. The method of claim 8, wherein the one or more symbol periods
are determined pseudo-randomly based on the received beacon symbol
timing information.
11. A wireless communications apparatus that transmits one or more
beacon symbols in different symbol periods or time slots of a
superframe in an OFDM configuration and on the same or different
subcarriers to mitigate collisions with beacon symbols from other
sectors and grow the number of available independent channels for
beacon symbol transmissions as a factor of the additional available
symbol periods, comprising: at least one processor configured to
select at least one symbol period and/or a subcarrier in a
superframe in an OFDM configuration for transmitting a beacon
symbol; and a memory coupled to the at least one processor.
12. The wireless communications apparatus of claim 11, wherein the
at least one processor is further configured to transmit beacon
symbols.
13. The wireless communications apparatus of claim 11, wherein the
at least one of the symbol period or the subcarrier is selected
based on information regarding other wireless communications
apparatuses sending beacon symbols.
14. The wireless communications apparatus of claim 13, wherein the
information is received in communication with one or more mobile
devices.
15. The wireless communications apparatus of claim 11, wherein the
symbol period and/or the subcarrier are chosen based at least in
part on an identifier related to the wireless communications
apparatus.
16. The wireless communications apparatus of claim 11, wherein a
plurality of symbol periods and/or subcarriers are selected in a
single superframe.
17. A wireless communications apparatus that transmits one or more
beacon symbols during different symbol periods or time slots of a
superframe in an OFDM configuration and on the same or different
subcarriers to mitigate collisions with beacon symbols from other
sectors to grow the number of available independent channels for
beacon symbol transmissions as a factor of the additional available
symbol periods, comprising: means for dividing a superframe into
one or more symbol periods; means for synchronously communicating
within the symbol periods; means for selecting one of the symbol
periods for transmitting a beacon symbol to avoid collision with a
second beacon symbol of another sector; and means for transmitting
the beacon symbol in the selected symbol period.
18. The wireless communications apparatus of claim 17, further
comprising means for selecting a subcarrier of the superframe for
transmitting the beacon symbol to avoid collision with the second
beacon symbol.
19. The wireless communications apparatus of claim 18, wherein the
subcarrier is selected using a maximum distance separable (MDS)
code.
20. The wireless communications apparatus of claim 17, further
comprising means for receiving information regarding the second
beacon symbol.
21. The wireless communications apparatus of claim 17, wherein at
least one of the beacon symbol or the one or more symbol periods
are chosen based at least in part on a identifier of a source of
the beacon symbol.
22. The wireless communications apparatus of claim 17, wherein the
one or more symbol periods are selected based at least in part on a
predetermined network planning configuration.
23. The wireless communications apparatus of claim 17, wherein the
one or more symbol periods are selected based at least in part on
beacon symbol timing information received regarding other
sectors.
24. The wireless communications apparatus of claim 23, wherein the
beacon symbol timing information is received by a mobile
device.
25. The wireless communications apparatus of claim 23, wherein the
one or more symbol periods are determined pseudo-randomly based on
the received beacon symbol timing information.
26. A computer program product, comprising: a non-transitory
computer-readable medium comprising: code for causing at least one
computer to determine a symbol period for sending a beacon symbol
in different symbol periods or time slots of a superframe in an
OFDM configuration and on different subcarriers and to reduce or
avoid collision with a second beacon symbol from a disparate
source, the symbol period being determined from a subset of symbol
periods useable for transmitting beacon symbols; and code for
causing the at least one computer to send the beacon symbol in the
determined symbol period.
27. The computer program product of claim 26, the computer-readable
medium further comprising: code for causing the at least one
computer to determine a subcarrier in the symbol period for sending
the beacon symbol; and code for causing the at least one computer
to send the beacon symbol on the subcarrier.
28. A wireless communication apparatus that transmits one or more
beacon symbols in different symbol periods or time slots of a
superframe in an OFDM configuration and on the same or different
subcarriers to mitigate collisions with beacon symbols from other
sectors and grow the number of available independent channels for
beacon symbol transmissions as a factor of the additional available
symbol periods, comprising: a processor configured to: divide a
superframe into one or more symbol periods; synchronously
communicate within the symbol periods; select one of the symbol
periods for transmitting a beacon symbol to avoid collision with a
second beacon symbol of another sector; and transmit the beacon
symbol in the selected symbol period; and a memory coupled to the
processor.
29. A method of receiving beacon symbols at multiple symbol periods
or time slots of a superframe in an OFDM configuration and on the
same or different subcarriers to mitigate collision with beacon
symbols from other sectors and grow the number of available
independent channels for beacon symbol transmissions as a factor of
the additional available symbol periods, comprising: receiving
beacon symbols from a plurality of transmitters, the beacon symbols
being sent in a symbol period selected to reduce collision with the
other transmitters; and decoding the received beacon symbols to
obtain information comprised in the beacon symbols.
30. The method of claim 29, wherein the transmitters relate to one
or more sectors of one or more base stations in a wireless
communications network.
31. The method of claim 30, further comprising transmitting beacon
symbol information to the sectors regarding other sectors such that
the other sectors can utilize the beacon symbol information in
selecting symbol periods for the beacon symbols.
32. The method of claim 29, wherein the obtained information
relates to one or more transmitter identifiers.
33. The method of claim 32, wherein at least one transmitter is a
sector and the obtained information further comprises an index of a
preferred carrier of the sector.
34. The method of claim 29, further comprising utilizing a timer to
associate synchronous timing with the beacon symbols to determine a
pattern or periodicity of the beacon symbols.
35. The method of claim 29, wherein the symbol periods of the
beacon symbols are pseudo-random with respect to at least one other
symbol period of a disparate beacon symbol.
36. A wireless communications apparatus that transmits one or more
beacon symbols in different symbol periods or time slots of a
superframe in an OFDM configuration and on the same or different
subcarriers to mitigate collisions with beacon symbols from other
sectors and grow the number of available independent channels for
beacon symbol transmissions as a factor of the additional available
symbol periods, comprising: at least one processor configured to
receive and decode a plurality of beacon symbols sent from one or
more sectors during different symbol periods in a synchronous
wireless communications network; and a memory coupled to the at
least one processor.
37. The wireless communications apparatus of claim 36, wherein the
at least one processor is further configured to use beacon code
information to decode the beacon symbols to obtain additional
information regarding the beacon symbols.
38. The wireless communications apparatus of claim 36, wherein the
at least one processor is further configured to decode the
plurality of beacon symbols yields at least one identifier for the
one or more sectors.
39. The wireless communications apparatus of claim 36, wherein the
at least one processor is further configured to transmit beacon
symbol information to the sectors regarding other sectors such that
the other sectors can utilize the beacon symbol information in
selecting symbol periods for the beacon symbols.
40. The wireless communications apparatus of claim 36, wherein the
at least one processor is further configured to utilize a timer to
associate synchronous timing with the plurality of beacon symbols
to determine a pattern or periodicity of the beacon symbols.
41. The wireless communications apparatus of claim 36, wherein
symbol periods of the beacon symbols are pseudo-random with respect
to at least one other symbol period of a disparate beacon
symbol.
42. A wireless communications apparatus for receiving beacon
symbols at multiple symbol periods or time slots of a superframe in
an OFDM configuration and on the same or different subcarriers to
mitigate collisions with beacon symbols from other sectors and grow
the number of available independent channels for beacon symbol
transmissions as a factor of the additional available symbol
periods, comprising: means for synchronously communicating in a
wireless communications network; means for receiving a first beacon
symbol in a first symbol period in a superframe; means for
receiving a second beacon symbol in a second symbol period of the
superframe; and means for decoding the first and second beacon
symbols to identify one or more sectors transmitting the beacon
symbols.
43. The wireless communications apparatus of claim 42, the decoding
of the first and second beacon symbols performed
asynchronously.
44. The wireless communications apparatus of claim 42, further
comprising means for transmitting beacon symbol information to the
one or more sectors regarding other sectors such that the one or
more sectors can utilize the beacon symbol information in selecting
symbol periods for beacon symbols.
45. The wireless communications apparatus of claim 42, further
comprising means for decoding the first and second beacon symbols
to identify an index of one or more preferred carrier of the one or
more sectors.
46. The wireless communications apparatus of claim 42, further
comprising means for utilizing a timer to associate synchronous
timing with the first and second beacon symbol to determine a
pattern or periodicity of the first and second beacon symbol.
47. The wireless communications apparatus of claim 42, wherein the
first symbol period is pseudo-random with respect to the second
symbol period.
48. A computer program product, comprising: a non-transitory
computer-readable medium comprising: code for causing at least one
computer to receive beacon symbols from a plurality of
transmitters, the beacon symbols being sent in a symbol in
different symbol periods or time slots of a superframe in OFDM
configuration and on different subcarriers to reduce collision with
the other transmitters; and code for causing the at least one
computer to decode the received beacon symbols to obtain
information comprised in the beacon symbols.
49. The computer program product of claim 48, wherein at least one
transmitter is a sector and the obtained information further
comprises an index of a preferred carrier of the sector.
50. A wireless communication apparatus that transmits one or more
beacon symbols in different symbol periods or time slots of a
superframe in OFDM configuration and on the same or different
subcarriers to mitigate collisions with beacon symbols from other
sectors and grow the number of available independent channels for
beacon symbol transmissions as a factor of the additional available
symbol periods, comprising: a processor configured to:
synchronously communicate in a wireless communications network;
receive a first beacon symbol in a first symbol period in a
superframe; receive a second beacon symbol in a second symbol
period of the superframe; and decode the first and second beacon
symbols to identify one or more sectors transmitting the beacon
symbols; and a memory coupled to the processor.
Description
BACKGROUND
I. Field
The following description relates generally to wireless
communications, and more particularly to orthogonalizing beacon
symbols in a wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide
various types of communication content such as, for example, voice,
data, and so on. Typical wireless communication systems may be
multiple-access systems capable of supporting communication with
multiple users by sharing available system resources (e.g.,
bandwidth, transmit power, . . . ). Examples of such
multiple-access systems may include code division multiple access
(CDMA) systems, time division multiple access (TDMA) systems,
frequency division multiple access (FDMA) systems, orthogonal
frequency division multiple access (OFDMA) systems, and the
like.
Generally, wireless multiple-access communication systems may
simultaneously support communication for multiple mobile devices.
Each mobile device may communicate with one or more base stations
via transmissions on forward and reverse links. The forward link
(or downlink) refers to the communication link from base stations
to mobile devices, and the reverse link (or uplink) refers to the
communication link from mobile devices to base stations. Further,
communications between mobile devices and base stations may be
established via single-input single-output (SISO) systems,
multiple-input single-output (MISO) systems, multiple-input
multiple-output (MIMO) systems, and so forth.
MIMO systems commonly employ multiple (N.sub.T) transmit antennas
and multiple (N.sub.R) receive antennas for data transmission. The
antennae can relate to both base stations (e.g. access points) and
mobile devices (e.g. access terminals) in one example, where the
base station can provide communication channels to the mobile
devices. Base stations can transmit beacon signals for
interpretation by the mobile devices in an attempt to identify the
base station and/or a transmission carrier or sector thereof. The
beacon symbols are sent at a given time in a superframe thus giving
way to beacon collision as the number of in-range sectors increases
beyond a number of available subcarriers.
SUMMARY
The following presents a simplified summary of one or more
embodiments in order to provide a basic understanding of such
embodiments. This summary is not an extensive overview of all
contemplated embodiments, and is intended to neither identify key
or critical elements of all embodiments nor delineate the scope of
any or all embodiments. Its sole purpose is to present some
concepts of one or more embodiments in a simplified form as a
prelude to the more detailed description that is presented
later.
In accordance with one or more embodiments and corresponding
disclosure thereof, various aspects are described in connection
with facilitating time shifting of beacon symbols sent by base
stations or sectors thereof. In particular, the beacon symbols can
be sent in different symbol periods of a superframe and on
different subcarriers to mitigate collision with beacon symbols
from other sectors. In this way, the number of available
independent channels for beacon symbol transmissions grows as a
factor of the additional available symbol periods.
According to related aspects, a method of transmitting beacon
symbols at different symbol periods is described herein. The method
can comprise determining a symbol period for sending a beacon
symbol to reduce or avoid collision with a second beacon symbol
from a disparate source, the symbol period being determined from a
subset of symbol periods useable for transmitting beacon symbols.
The method can also comprise sending the beacon symbol in the
determined symbol period.
Another aspect relates to a wireless communications apparatus. The
wireless communications apparatus can include at least one
processor configured to select at least one symbol period and/or a
subcarrier in a superframe for transmitting a beacon symbol. The
wireless communications apparatus can also include a memory coupled
to the at least one processor.
Yet another aspect relates to a wireless communications apparatus
that transmits one or more beacon symbols during different symbol
periods of a superframe. The wireless communications apparatus can
include means for dividing a superframe into one or more symbol
periods and means for synchronously communicating within the symbol
periods. The wireless communications apparatus can also include
means for selecting one of the symbol periods for transmitting a
beacon symbol to avoid collision with a second beacon symbol of
another sector as well as means for transmitting the beacon symbol
in the selected symbol period.
Still another aspect relates to a computer program product, which
can have a computer-readable medium including code for causing at
least one computer to determine a symbol period for sending a
beacon symbol to reduce or avoid collision with a second beacon
symbol from a disparate source, the symbol period being determined
from a subset of symbol periods useable for transmitting beacon
symbols. The code can also cause the at least one computer to send
the beacon symbol in the determined symbol period.
In accordance with another aspect, an apparatus in a wireless
communication system can include a processor configured to divide a
superframe into one or more symbol periods, synchronously
communicate within the symbol periods, select one of the symbol
periods for transmitting a beacon symbol to avoid collision with a
second beacon symbol of another sector, and transmit the beacon
symbol in the selected symbol period. Also, the apparatus can
include a memory coupled to the processor.
According to a further aspect, a method of receiving beacon symbols
at multiple symbol periods is described herein. The method can
comprise receiving beacon symbols from a plurality of transmitters,
the beacon symbols being sent in a symbol period selected to reduce
collision with the other transmitters. The method can additionally
comprise decoding the received beacon symbols to obtain information
comprised in the beacon symbol.
Another aspect relates to a wireless communications apparatus. The
wireless communications apparatus can include at least one
processor configured to receive and decode a plurality of beacon
symbols sent from one or more sectors during different symbol
periods in a synchronous wireless communications network. The
wireless communications apparatus can also include a memory coupled
to the at least one processor.
Yet another aspect relates to a wireless communication apparatus
for receiving beacon symbols at multiple symbol periods. The
apparatus can comprise means for synchronously communicating in a
wireless communications network. The apparatus can also include
means for receiving a first beacon symbol in a first symbol period
in a superframe and means for receiving a second beacon symbol in a
second symbol period of the superframe. The apparatus can further
comprise means for decoding the first and second beacon symbols to
identify one or more sectors transmitting the beacon symbols.
Still another aspect relates to a computer program product, which
can have a computer-readable medium including code for causing at
least one computer to receive beacon symbols from a plurality of
transmitters, the beacon symbols being sent in a symbol period
selected to reduce collision with the other transmitters. The code
can also cause the at least one computer to decode the received
beacon symbols to obtain information comprised in the beacon
symbols.
In accordance with another aspect, an apparatus can be provided in
a wireless communication system including a processor configured to
synchronously communicate in a wireless communications network. The
processor can also be configured to receive a first beacon symbol
in a first symbol period in a superframe and receive a second
beacon symbol in a second symbol period of the superframe.
Moreover, the processor can also be configured to decode the first
and second beacon symbols to identify one or more sectors
transmitting the beacon symbols. Additionally, the apparatus can
comprise a memory coupled to the processor.
To the accomplishment of the foregoing and related ends, the one or
more embodiments comprise the features hereinafter fully described
and particularly pointed out in the claims. The following
description and the annexed drawings set forth in detail certain
illustrative aspects of the one or more embodiments. These aspects
are indicative, however, of but a few of the various ways in which
the principles of various embodiments may be employed and the
described embodiments are intended to include all such aspects and
their equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration of a wireless communication system in
accordance with various aspects set forth herein.
FIG. 2 is an illustration of an example communications apparatus
for employment within a wireless communications environment.
FIG. 3 is an illustration of an example wireless communications
system that effectuates transmitting beacon symbols on different
symbol periods.
FIG. 4 is an illustration of example superframes and symbol periods
utilized in wireless communications systems.
FIG. 5 is an illustration of an example wireless communications
network.
FIG. 6 is an illustration of an example methodology that
facilitates transmitting beacon symbols at different symbol
periods.
FIG. 7 is an illustration of an example methodology that
facilitates receiving beacon symbols transmitted in different
symbol periods.
FIG. 8 is an illustration of an example mobile device that
facilitates receiving beacon symbols broadcast at different times
in a superframe.
FIG. 9 is an illustration of an example system that facilitates
broadcasting beacon symbols in various symbol periods.
FIG. 10 is an illustration of an example wireless network
environment that can be employed in conjunction with the various
systems and methods described herein.
FIG. 11 is an illustration of an example system that transmits
beacon symbols using multiple symbol periods of a superframe.
FIG. 12 is an illustration of an example system that receives a
plurality of beacon symbols sent at different time periods of a
superframe.
DETAILED DESCRIPTION
Various embodiments are now described with reference to the
drawings, wherein like reference numerals are used to refer to like
elements throughout. In the following description, for purposes of
explanation, numerous specific details are set forth in order to
provide a thorough understanding of one or more embodiments. It may
be evident, however, that such embodiment(s) can be practiced
without these specific details. In other instances, well-known
structures and devices are shown in block diagram form in order to
facilitate describing one or more embodiments.
As used in this application, the terms "component," "module,"
"system," and the like are intended to refer to a computer-related
entity, either hardware, firmware, a combination of hardware and
software, software, or software in execution. For example, a
component can be, but is not limited to being, a process running on
a processor, a processor, an object, an executable, a thread of
execution, a program, and/or a computer. By way of illustration,
both an application running on a computing device and the computing
device can be a component. One or more components can reside within
a process and/or thread of execution and a component can be
localized on one computer and/or distributed between two or more
computers. In addition, these components can execute from various
computer readable media having various data structures stored
thereon. The components can communicate by way of local and/or
remote processes such as in accordance with a signal having one or
more data packets (e.g., data from one component interacting with
another component in a local system, distributed system, and/or
across a network such as the Internet with other systems by way of
the signal).
Furthermore, various embodiments are described herein in connection
with a mobile device. A mobile device can also be called a system,
subscriber unit, subscriber station, mobile station, mobile, remote
station, remote terminal, access terminal, user terminal, terminal,
wireless communication device, user agent, user device, or user
equipment (UE). A mobile device can be a cellular telephone, a
cordless telephone, a Session Initiation Protocol (SIP) phone, a
wireless local loop (WLL) station, a personal digital assistant
(PDA), a handheld device having wireless connection capability,
computing device, or other processing device connected to a
wireless modem. Moreover, various embodiments are described herein
in connection with a base station. A base station can be utilized
for communicating with mobile device(s) and can also be referred to
as an access point, Node B, or some other terminology.
Moreover, various aspects or features described herein can be
implemented as a method, apparatus, or article of manufacture using
standard programming and/or engineering techniques. The term
"article of manufacture" as used herein is intended to encompass a
computer program accessible from any computer-readable device,
carrier, or media. For example, computer-readable media can include
but are not limited to magnetic storage devices (e.g., hard disk,
floppy disk, magnetic strips, etc.), optical disks (e.g., compact
disk (CD), digital versatile disk (DVD), etc.), smart cards, and
flash memory devices (e.g., EPROM, card, stick, key drive, etc.).
Additionally, various storage media described herein can represent
one or more devices and/or other machine-readable media for storing
information. The term "machine-readable medium" can include,
without being limited to, wireless channels and various other media
capable of storing, containing, and/or carrying instruction(s)
and/or data.
Referring now to FIG. 1, a wireless communication system 100 is
illustrated in accordance with various embodiments presented
herein. System 100 comprises a base station 102 that can include
multiple antenna groups. For example, one antenna group can include
antennas 104 and 106, another group can comprise antennas 108 and
110, and an additional group can include antennas 112 and 114. Two
antennas are illustrated for each antenna group; however, more or
fewer antennas can be utilized for each group. Base station 102 can
additional include a transmitter chain and a receiver chain, each
of which can in turn comprise a plurality of components associated
with signal transmission and reception (e.g., processors,
modulators, multiplexers, demodulators, demultiplexers, antennas,
etc.), as will be appreciated by one skilled in the art.
Base station 102 can communicate with one or more mobile devices
such as mobile device 116 and mobile device 122; however, it is to
be appreciated that base station 102 can communicate with
substantially any number of mobile devices similar to mobile
devices 116 and 122. Mobile devices 116 and 122 can be, for
example, cellular phones, smart phones, laptops, handheld
communication devices, handheld computing devices, satellite
radios, global positioning systems, PDAs, and/or any other suitable
device for communicating over wireless communication system 100. As
depicted, mobile device 116 is in communication with antennas 112
and 114, where antennas 112 and 114 transmit information to mobile
device 116 over a forward link 118 and receive information from
mobile device 116 over a reverse link 120. Moreover, mobile device
122 is in communication with antennas 104 and 106, where antennas
104 and 106 transmit information to mobile device 122 over a
forward link 124 and receive information from mobile device 122
over a reverse link 126. In a frequency division duplex (FDD)
system, forward link 118 can utilize a different frequency band
than that used by reverse link 120, and forward link 124 can employ
a different frequency band than that employed by reverse link 126,
for example. Further, in a time division duplex (TDD) system,
forward link 118 and reverse link 120 can utilize a common
frequency band and forward link 124 and reverse link 126 can
utilize a common frequency band.
Each group of antennas and/or the area in which they are designated
to communicate can be referred to as a sector of base station 102.
For example, antenna groups can be designed to communicate to
mobile devices in a sector of the areas covered by base station
102. In communication over forward links 118 and 124, the
transmitting antennas of base station 102 can utilize beamforming
to improve signal-to-noise ratio of forward links 118 and 124 for
mobile devices 116 and 122. Also, while base station 102 utilizes
beamforming to transmit to mobile devices 116 and 122 scattered
randomly through an associated coverage, mobile devices in
neighboring cells can be subject to less interference as compared
to a base station transmitting through a single antenna to all its
mobile devices.
In one example, the base station 102 can send a beacon symbol from
each antenna 104, 106, 108, 110, 112, and 114, and/or a grouping of
antennae comprising information regarding the antenna and/or
corresponding base station 102, such as identification information
and/or other metrics or general information associated with the
antennae and/or base station 102. According to an example, a beacon
symbol can be a portion of a signal that is transmitted with
substantial power to signal a small message to one or more mobile
devices 116 and 122 that can have very low signal to noise ratios
(due to distance or other interference, for example). The mobile
devices 116 and 122 can receive one or more beacon symbols to
discern information related to the antennae and/or base station
102; in one example, the beacon symbol can be one of the first
signals the mobile devices 116 and 122 can interpret regarding a
base station 102 or antenna. To this end, a beacon symbol can be
sent so that it is easily identifiable by the mobile devices 116
and 122. According to an example, the base station 102 can send a
beacon symbol from a given antenna 104, 106, 108, 110, 112, and/or
114 by transmitting substantially all available power on a single
subcarrier channel thereof (or a small number of channels). The
mobile devices 116 and/or 122 can receive the signal and perform a
fast Fourier transform (FFT), or other decoding algorithm, on the
signal to determine that one channel has a very high energy as
compared to the others. The mobile devices 116 and/or 122 can
conclude that this is a beacon symbol related to a given antenna
and/or base station 102 and interpret the symbol accordingly.
To facilitate operability with a plurality of antennas (as shown in
the figure) and/or a plurality of base stations (not shown), the
base station 102 can time shift the beacon symbols to avoid
collision and confusion. For example, one antenna 104 can transmit
beacon symbols on a different timeslot from antenna 114 (or another
antenna for another base station, for example). Additionally, the
base station 102 can transmit the beacon symbols on different
subcarriers of a bandwidth each time and/or according to a pattern
of subcarriers and/or time slots. To this end, beacon symbols can
also be a pattern of multiple symbols, each of which must be
interpreted to obtain relevant information, as well. Moreover, in
one example, the pattern or sequence can be comprised within one or
more superframes (e.g. a frame of predetermined time duration).
While orthogonalization of beacons related to one or more antennas
of a base station 102 can be implemented within the base station
102, the subject matter described herein additionally facilitates
orthogonalizing beacons between different base stations and/or
sectors thereof. The foregoing aspects can facilitate
orthogonalization of many distinct combinations of beacon symbols
even where a number of sectors available in an area exceed the
number of subcarriers that exist for the available bandwidth. In
this regard, the sectors can transmit associated beacon symbols
while minimizing collision, for example. Additionally, by
orthogonalizing beacon symbols, the base station 102 can devote
substantially all power to beacon symbols for each antenna
associated therewith. In one example, it is to be appreciated that
other data can be sent (e.g. other OFDM symbols can be utilized)
when sending a beacon symbol in a symbol period.
According to an example, system 100 can be a multiple-input
multiple-output (MIMO) communication system. Further, system 100
can utilize any type of duplexing technique to divide communication
channels (e.g., forward link, reverse link, . . . ) such as FDD,
TDD, and the like. In one example, the system 100 can be an OFDMA
system where symbols can be transmitted over a given frequency for
a time period. Moreover, system 100 can be synchronous in one
example, such that the base station 102, mobile devices 116 and
122, and/or other devices can have a time, clock, or other aspects
to synchronize communications between the devices. This behavior,
in one example, can facilitate time shifting of the beacon symbols,
as described above, as the base station 102 can transmit the beacon
symbols at given times and the mobile devices 116 and 122 can
interpret the time sent and utilize that information to process
subsequent beacon symbols or other transmissions. In one example,
the base station 102 can transmit beacon symbols on determined
symbol periods (and such can be communicated in a beacon symbol in
one example) and the mobile devices 116 and 122 can utilize this
information along with their own clock/timer to discern when a
signal is a beacon symbol and/or when to expect such (e.g. in which
superframe). In one example, a beacon can be transmitted according
to a plurality of disparate beacon symbols (e.g. a beacon code) in
one or more superframes. These can be time shifted within the
superframe or about multiple superframes, and the code can be
different at disparate points in time (such as within different
superframes, etc.). Using information derived from the beacon
symbols, a pattern of beacon symbols, and/or the timing of such,
the mobile devices 116 and 122 can determine other information
regarding the base station 102 and/or a broadcasting sector
thereof. For example, the mobile devices 116 and 122 can come to
recognize the beacon symbol of the base station 102, or a sector
thereof, and determine the location of the superframe preamble for
the base station 102 or sector. Other information, including the
size of the superframe, identifying information, signal strength,
signal quality, frequency, bandwidth capabilities, and
substantially any information regarding the beacon, the base
station 102, and/or the sector can be determined in part by the
beacon symbol, for example.
Turning to FIG. 2, illustrated is a communications apparatus 200
for employment within a wireless communications environment. The
communications apparatus 200 can be a base station or a portion
thereof, a mobile device or a portion thereof, or substantially any
communications apparatus that transmits one or more beacon symbols.
The communications apparatus 200 can include a timer 202 that
facilitates operating in a synchronized environment, a beacon
symbol assignor 204 that selects a subcarrier in a bandwidth
(and/or a time slot) for transmitting a beacon symbol (such as a
beacon OFDM symbol), and a transmitter 206 that broadcasts the
beacon symbol. In one example, the communications apparatus 200 can
formulate a beacon symbol and assign it to a certain time slot in a
superframe, for example, using the beacon symbol assignor 204. The
beacon symbol can be broadcast using the transmitter 206 and
leveraging the timer 202 to ensure the assigned time slot is used
for the broadcast. It is to be appreciated that where the
communications apparatus is a base station or other access point,
it can have one or more transmitters 206, for example.
In one example, the timer 202 can keep a system time related to a
wireless communication system to facilitate synchronized
communicating therein. Devices communicating within the system can
utilize the timer 202 to ensure accuracy of the time based
communications. This allows communications apparatus 200 (or a
plurality of such) to transmit beacon symbols in one or more symbol
periods of a given superframe, for example. The beacon symbol
assignor 204 can utilize the timer 202 to transmit the beacon
symbol on a selected time slot or OFDM symbol. In this regard,
other communications apparatuses receiving the beacon symbol can
discern the time in the superframe and expect to receive a beacon
symbol during that time or another time that can be indicated in
the beacon symbol, handling such accordingly. To this end, the
beacon symbol assignor 204 can select a specific subcarrier for
transmission of one or more beacon symbols; for example, the
subcarrier can be assigned per an antenna to which the beacon
symbol relates. According to an example, the selection of the
subcarrier can be based on network planning such that
communications apparatuses situated near to one another (where the
signals transmitted could be received by a single device) can
select disparate subcarriers for the beacon symbols to allow a
receiving device to distinguish the apparatuses. It is to be
appreciated, however, that different subcarriers can be used by a
single communications apparatus for transmission of a beacon symbol
in different time slots or superframes and/or a pattern of
subcarriers can be used as well.
According to another example, the beacon symbols transmitted by the
communications apparatus 200 can be time shifted as well to prevent
collision with other signals sent by the communications apparatus
200 or other communications apparatuses (including mobile devices,
access points, etc. as mentioned above). This can be inherently
useful as it provides flexibility in the communications system as
well as useful where a number of sectors that overlap for a given
area can be greater than subcarriers available in a bandwidth used
to communicate by the sectors, for example. According to one
example, neighboring communications apparatuses (or apparatuses
with overlapping coverage areas) can be assigned different time
slots and/or different subcarriers for transmitting beacon symbols.
To this end, the beacon symbol assignor 204 of each communications
apparatus 200 can ensure the correct time slot and/or subcarrier
(and/or tone) is selected by leveraging the timer 202 to determine
time. The transmitter 206 can transmit the beacon symbol at the
appropriate time.
As described, the beacon symbol assignor 204 can assign disparate
time slots and/or subcarriers to different communications
apparatuses to mitigate collision and confusion in beacon symbol
transmission. The time slot and/or subcarrier can be assigned
during network planning, in one example, such that neighboring
sectors can transmit beacons on different time slots and/or
subcarriers without colliding. In another example, the time slots
and/or subcarriers can be assigned similarly to assignment of
carriers to sectors (e.g. frequency reuse). In a further example,
the time slots and/or subcarriers can be assigned randomly and/or
pseudo-randomly (e.g. such that only a given number of periods in a
superframe or subcarriers can be used for beacon symbols or for
beacon symbols for that given communications apparatus). In this
regard, for example, a subset of periods in the superframe and/or a
subset of subcarriers can be selected for randomization for a given
communications apparatus 200, and other communications apparatuses
in range of the communications apparatus 200 can be assigned a
different subset of symbol periods and/or subcarriers to randomize
to further mitigate the chance of collision. Moreover, time slots
and/or subcarriers can be assigned from a device within a network
to which the communications apparatus 200 relates (e.g. based on an
identifier, model, antenna grouping, range, surrounding
communications apparatuses, and/or other metric associated with the
communications apparatus 200). In addition, time slots and/or
subcarriers can be assigned in real-time by a device that can
communicate with the beacon symbol assignor 204, such as the
network device. Further, the time slot and subcarrier information
can be pulled by the communications apparatus 200 from another
device or apparatus and/or determined using inference technology
regarding neighboring sectors. In one embodiment, the information
regarding the neighboring sectors can be received by a mobile
device moving about the sectors, a network that connects or
utilizes the sectors, directly from the sectors, and/or the like.
In this example, the communications apparatus 200 can report back
(and/or negotiate) its beacon time slot(s) and/or subcarrier(s). It
is to be appreciated that the time slots can be assigned using one
or more of the aforementioned aspects, and the subcarriers can be
assigned using the same or a different aspect.
However determined, the beacon symbol assignor 204 can leverage the
timer 202 and transmitter 206 to ensure the beacon symbol, or
symbols, is/are properly transmitted. As mentioned, the beacon
symbol assignor 204 can assign the time slots and subcarriers in
substantially any available combination. For example, the beacon
symbol assignor 204 can assign one beacon symbol to one subcarrier
of one time slot or period in a superframe for communications
apparatus 200. The subcarriers and/or periods used can be different
for other beacon symbols from other communications apparatuses, for
example. According to another example, the communications apparatus
200 can be assigned (or can request, for example) a plurality of
time slots and/or subcarriers to be used in sending a beacon. In
this example, the beacon can be a pattern of beacon symbols (e.g. a
beacon code) where the symbols are received in totality by a device
reading the broadcast to interpret the beacon symbol. It is to be
appreciated that, in this example, by using multiple time slots in
a superframe, the time needed for a device to interpret a beacon
code can be lessened as the entire, or at least more than one
symbol in the code, can be transmitted in a single superframe.
As described previously, the communications apparatus 200 can have
multiple transmitters 206, where each transmitter 206 can send a
disparate beacon. In this regard, the communications apparatus 200
can time shift the beacon symbols and transmit the beacons on
disparate subcarriers of bandwidth. In this regard, substantially
all the power of the communications apparatus 200 can be used to
transmit the beacon symbols as substantially no other subcarriers
are used for the time slot. It is to be appreciated that a small
number of subcarriers can be used as well, but other transmissions
can be pushed to the next non-beacon time slot. Alternatively, the
beacons can transmit on disparate subcarriers in the same time slot
or period, in which case the power of the communications apparatus
200 can be split among the transmitters 206 for broadcasting
beacons.
Moreover, although not shown, it is to be appreciated that
communications apparatus 200 can include memory that retains
instructions with respect to assigning a beacon symbol time slot
and/or subcarrier based on the aforementioned determinations and in
at least one of the aforementioned configurations. Further,
communications apparatus 200 can include a processor that can be
utilized in connection with executing instructions (e.g.,
instructions retained within memory, instructions obtained from a
disparate source, . . . ).
Now referring to FIG. 3, illustrated is a wireless communications
system 300 that effectuates orthogonal transmission of beacon
symbols. System 300 includes a base station 302 that communicates
with a mobile device 304 (and/or any number of disparate mobile
devices (not shown)). Base station 302 can transmit information to
mobile device 304 over a forward link channel; further base station
302 can receive information from mobile device 304 over a reverse
link channel. Moreover, system 300 can be a MIMO system.
Additionally, the system 300 can operate in an OFDMA wireless
network, in one example.
Base station 302 can include a timer 306 that is synchronized
throughout the system 300 to facilitate synchronized communication,
a beacon symbol assignor 308 that assigns a beacon and/or a
plurality of symbols related thereto to one or more time slots of a
superframe and/or subcarriers of bandwidth, and an encoder 310 that
transforms the communication into a time domain, such as by using
an inverse fast Fourier transform (IFFT), for example. Additionally
or alternatively, the encoder 310 can convert a sector identifier
to a beacon code (e.g. a pattern of beacon symbols), for instance.
In one example, the beacon symbol assignor 308 can select a
subcarrier for transmission of the beacon symbol, and the encoder
310 can transform the beacon symbol into a sector identifier and/or
to a time domain. The beacon symbol assignor 308 can select a time
slot for transmitting the beacon symbol as described supra, and the
base station 300 can leverage the timer 306 to transmit the beacon
symbol during the appropriate time. In this regard, the system 300
can allow synchronous communication between the base station 302
and the mobile device 304.
The mobile device 304 can comprise a timer 312 that facilitates
synchronous communication in a wireless communication network, for
example, and a decoder 314 that decodes messages received from
other network entities. According to one example, the mobile device
304 can receive a beacon symbol (or other data transmission) and
decode it using the decoder 314. The decoder 314 can also determine
a sector based in part on a beacon symbol or plurality of such
forming a pattern/beacon code, for example. Additionally, the
mobile device 304 can leverage its timer 312 to determine
additional information regarding the transmission. For example,
beacon symbols can be sent at certain given time slots in which
case the mobile device 304 can discern whether a transmission is a
beacon symbol or not based on the time slot determined by the timer
312.
According to an example, the encoder 310 can create a beacon code
(e.g. a sequence of beacon symbols) related to a sector identifier
of the base station 302. The beacon symbol assignor 308 can assign
one or more subcarriers on one or more time slots for transmitting
a portion of the beacon code. Additionally, the encoder 310 can
transform the beacon code, or a portion thereof (such as the
transmitted portion) to a time domain (e.g. such as by performing
an IFFT). Utilizing the timer 306, the base station 302 can
broadcast the beacon according to the beacon code. The mobile
device 304 can receive the broadcast and utilize the decoder 314 to
perform an FFT on the broadcast to transform the symbols of the
bandwidth to the frequency domain. This will yield one symbol, or a
small number of symbols, with substantially more energy than the
others indicating a beacon symbol. The timer 312 can be utilized to
discern a receive time for the beacon symbol. Using additional
information in the beacon, the mobile device 304 can identify a
sector to which the beacon belongs, for example; this information
can also be discerned by the decoder 314 in an example. Where the
beacon is a code of symbols disparately broadcast, the mobile
device 304 can decode the plurality of symbols as they arrive and
utilize the timer 312 to discern timing of the beacon symbols.
Using this information, the mobile device 304 can identify the
source of the beacon and/or other information regarding the source.
Additionally, the mobile device 304 can identify the location of a
related superframe preamble for use with subsequent beacon and
non-beacon transmissions from the base station 302 or sector, for
instance. In this regard, the mobile device 304 can comprise valid
beacon symbols or beacon codes that can be recognized by the mobile
device 304 (these can be stored in a memory, for example).
Now referring to FIG. 4, a representation of two bandwidths over a
period of time 400 is displayed for two disparate transmitters. The
bandwidth is represented by a plurality of subcarriers for given
symbol periods 402, 406, 410, 414, 418, and 422 and the time period
can be separated into one or more superframes 426, which can have
predetermined time durations for example. Each of the shown symbol
periods 402, 406, 410, 414, 418, and 422 can broadcast beacon
symbols 404, 408, 412, 416, 420, and 424, respectively, represented
as substantially the only subcarrier in the symbol period utilizing
power (which can be substantially all the power that is available
since the other subcarriers are not powered). As shown, the beacon
symbol 404, 408, and/or 412 can be transmitted on different
subcarriers and/or at different time periods each superframe.
Moreover, the beacon symbols for the second transmitter 416, 420,
and 424 can be broadcast at different symbol periods to
disambiguate the symbols from those of the first transmitter. In
one example, though not shown, the transmitters can use
substantially the same beacon code (e.g. plurality of beacon
symbols in sequence). In this example, transmitting the symbols at
different symbol periods can mitigate confusion between the two
transmitters sending substantially the same beacon code, for
example. It is to be appreciated that multiple beacon symbols can
be transmitted per superframe; also, one or more superframes can be
skipped and not transmit a beacon symbol as well.
According to an example, the beacon symbols 404, 408, and 412 can
relate to the same or different sectors for a given base station,
one or more carriers for a single sector, and/or the like.
Additionally, beacon symbols 416, 420, and 424 can relate to a
disparate sector and/or transmitter/carrier within a given base
station or a different base station all together, for example. In
this regard, the beacon symbols 404, 408, and 412 can be chosen
based on an identifier of the base station or sector (e.g., sector
ID, etc.). For instance, the base station can have a plurality of
transmitters that facilitate communication in a plurality of
sectors, and a beacon symbol is sent for each sector in a different
subcarrier, time period, and/or superframe. In another example, a
sector can have a number of carriers that can send beacon symbols
as well. Thus, the beacon symbol 404 can relate to a sector or
carrier, 408 to another, 412 to another, and so on. In one example,
the beacon symbols can be transmitted within one or more
superframes using multiple OFDM symbols within the superframes,
though not shown in this figure. Additionally, the same or
different subcarriers can be used for each transmission for a given
sector; the subcarriers can be rotated between the sectors in one
example as well. Also, the time slots can be the same or different
in each superframe or sequence of superframes for the given
sectors, for example. According to another example, transmissions
can be sent by the base stations in the time periods, and punctured
when a beacon symbol needs to be transmitted.
In another example, the beacon symbols 404, 408, and 412, can
relate to a single sector of a base station that transmits a beacon
in each of the three displayed superframes or transmits the
multiple beacon symbols as a portion of a beacon code as described
previously. In this regard, the beacon symbols 416, 420, and 424
can relate to another beacon code. In one example, at least one of
the beacon symbols 404, 408, and/or 412 (as well as 416, 420,
and/or 424) can provide information regarding the timing and/or
subcarriers used in transmitting subsequent symbols in the beacon
code. It is to be appreciated that more than one base station can
provide a substantially similar code; to mitigate confusion, the
codes can be offset according to timeslot/symbol period of a
superframe as described herein such that the symbols are not
received at competing times by devices in the transmission area of
the one or more base stations. Although not shown, the two beacons
(or more beacons) can overlap with respect to some symbols (e.g.,
beacon symbols of disparate sectors can overlap). Moreover, though
not shown, multiple beacon symbols related to a beacon (e.g., of a
sector, base station, mobile device, etc.) can be chosen to
transmit in a single superframe as well.
In one example, a superframe 426 can have 256 usable subcarriers
(e.g. OFDM symbols), such as that shown at 408, for a given symbol
period, such as 406. Additionally, 512 sectors (or another number
greater than 256) can transmit in a given area; in this example,
using time shifts along with the 256 subcarriers to transmit beacon
symbols can facilitate transmitting beacon symbols for all sectors
without conflict. To this end, the sectors can utilize a time
shifting configuration as described previously, including network
planning before or during base station deployment, communications
between the sectors regarding claimed or assigned time slots,
information received from other devices, such as mobile devices,
regarding beacon slots of other sectors, information about the
sectors themselves, such as an identifier, and the like, for
example.
Turning now to FIG. 5, a multi-cell layout 500 in a wireless
communication network is shown. The network can comprise a
plurality of base stations 502 having one or more transmission
carriers or sectors; for example, as shown each base station can
have 3 sectors, each of which can be assigned a specific carrier.
In this figure, the adjacent sectors are shown using different
carriers to mitigate interference within the sectors, for example.
This can be referred to as frequency reuse having a factor of 3,
for instance. In this regard, a carrier can be referred to as a
range of frequencies used by a sector to transmit a waveform.
Beacon symbols in such a network configuration can be transmitted
with or without reusing frequencies; for example, one carrier of
the base station 502 can transmit a beacon symbol, or more than one
carrier can transmit such. Additionally, data transmission can
utilize such configurations as well creating some possible
combinations of beacon and data use of carriers. In one example,
both data and beacon symbols can be transmitted on a single
carrier. This can reduce overhead for the beacon symbols as a
preferred carrier can be used for both beacons and data. In another
example, the beacon symbols can transmit on more than one carrier
with the data on a single carrier. This configuration can allow
mobile devices to detect beacons on the different carriers without
interrupting current communications on a data carrier.
Additionally, greater power can be given to the beacon symbol (e.g.
facilitating pilot detection by out-of-band devices), in one
example, as the data transmissions are not interrupted to allow
transmission of the beacon. It is to be appreciated that other
configurations are possible as well, such as the converse of the
aforementioned configuration as well as having data and beacons use
more than one of the available sectors for transmission.
As described previously, beacon symbols can be sent utilizing the
same or different subcarriers and/or the same or different symbol
periods and/or time slots (e.g. per superframe). The beacon symbol
can comprise information regarding a sector identifier and/or
another type of identifier (such as a pseudo-random number, a group
identifier, one or more sector or carrier identifiers, preferred
carrier index, and the like), for example. In one example, the
beacon for a given sector or carrier can comprise one or more
beacon symbols formulating a beacon code or pattern. Substantially
any code can be used for the beacon where zero to many beacon
symbols can be transmitted per superframe for a given number of
superframes. One such code can entail using a maximum distance
separable (MDS) code to transmit beacon symbols forming a beacon.
The MDS code can be formulated, in one example, by evaluating at
least one of the length of the beacon message (e.g. in bits), the
number of subcarriers available to transmit the beacon, the amount
of redundancy desired for the beacon message, the length of the
sequence of non-binary symbols, and/or additional similar
factors.
According to an example, 256 subcarriers can be available for
transmitting a beacon from a base station 502 where the beacon can
be a 12-bit message (including data as described previously); thus,
because a sector can transmit non-binary symbols, the MDS code can
be required to support at least 2^12=4096 different sequences of
non-binary symbols. In one example, the beacon symbols can be
transmitted at different times denoted by the index t, where
0.ltoreq.t<.infin.. For these symbols, the beacon can be
transmitted on a subcarrier with an index X.sub.t(.alpha..sub.1,
.alpha..sub.2), which can be expressed as:
X.sub.t(.alpha..sub.1,.alpha..sub.2)=p.sub.1.sup..alpha..sup.1.sup.+16t.s-
ym.p.sub.2.sup..alpha..sup.2.sup.+.alpha..sup.1.sup.+16t, where
p.sub.1 and p.sub.2 can be primitive elements of field Z.sub.257
(which can comprise 257 elements representing the subcarriers),
.alpha..sub.1 and .alpha..sub.2 can be exponent factors determined
based at least in part on the beacon message (as described infra),
and .sym. denotes modulo addition. In this example, p.sub.1 and
p.sub.2 can represent elements of Z.sub.257 that can generate all
256 non-zero elements of the field. In a more trivial example,
Z.sub.257 can have 5 as a primitive element as 5 can used to
generate all 6 non-zero elements (5.sup.0 mod 7=1, 5.sup.1 mod 7=5,
5.sup.2 mod 7=4, 5.sup.3 mod 7=6, 5.sup.4 mod 7=2, and 5.sup.5 mod
7=3). Additionally, the exponent factors .alpha..sub.1 and
.alpha..sub.2 can be defined as: 0.ltoreq..alpha..sub.1<16
0.ltoreq..alpha..sub.2<256. Thus, a total of 16*256=4096
disparate combinations of .alpha..sub.1 and .alpha..sub.2 can be
defined by the equation; this can support the 12-bit message having
4096 available sequences, for example. Additionally, each unique
combination of .alpha..sub.1 and .alpha..sub.2 can correspond to a
different message (and thus a different sequence of non-binary
symbols for the beacon) in this regard. In an example, a message
can be mapped to the available symbols in substantially any manner
including randomly, static assignment via network planning or
configuration, historical based, and the like. According to one
example, for a given combination of .alpha..sub.1 and
.alpha..sub.2, the message, M, can be mapped to
M=256*.alpha..sub.1+.alpha..sub.2, for example. Because
p.sub.i.sup.256=1, for i=1, 2, the code of the aforementioned
equation can be periodic with a period of 256/16=16 symbols; thus,
X(.alpha..sub.1, .alpha..sub.2)=X.sub.t+16(.alpha..sub.1,
.alpha..sub.2) for a given value of t, in one example. The beacon
symbols can be shifted according to time and subcarrier in this
way.
According to another example using a Reed-Solomon code, 211
subcarriers can be available for transmitting beacon symbols (e.g.
n=211 at 402) where the beacon symbol can be a 12-bit message
(including data as described previously); thus, the Reed-Solomon
code can be required to support at least 2^12=4096 different
sequences of non-binary symbols (which is what the sector
transmits, for instance). According to this example, the beacon
symbols can be transmitted on a subcarrier with an index
X.sub.t(.alpha..sub.1, .alpha..sub.2), which can be expressed as:
X.sub.t(.alpha..sub.1,.alpha..sub.2)=p.sub.1.sup..alpha..sup.1.sup.+21t.s-
ym.p.sub.1.sup..alpha..sup.2p.sub.2.sup.21t, where p.sub.1 can be a
primitive element of field Z.sub.211 (which can comprise 211
elements representing the subcarriers) and p.sub.2=p.sub.1.sup.2,
.alpha..sub.1 and .alpha..sub.2 can be exponent factors determined
based at least in part on the beacon message (as described infra),
and .sym. denotes modulo addition. In this example, p.sub.1=207 and
p.sub.2=p.sub.1.sup.2=16. Other primitive elements can be used for
p.sub.1 in other examples. A larger primitive element can provide
more frequency diversity since a small value of p.sub.1 can imply
that p.sub.1.sup.q.quadrature.t and p.sub.1.sup.q.quadrature.(t+1)
are close together. The selection of p.sub.2=p.sub.1.sup.2 can
result in the Reed-Solomon code, which can be characterized by a
weighted sum of increasing exponentials.
The exponent factors .alpha..sub.1 and .alpha..sub.2 can be defined
as: 0.ltoreq..alpha..sub.1<21, and
0.ltoreq..alpha..sub.2<210. Thus, a total of 21*210=4410
disparate combinations of .alpha..sub.1 and .alpha..sub.2 can be
defined by the equation; this can support the 12-bit message having
4096 available sequences, for example. Additionally, each unique
combination of .alpha..sub.1 and .alpha..sub.2 can correspond to a
different message (and thus a different sequence of non-binary
symbols for the beacon) in this regard. In an example, a message
can be mapped to the available symbols in substantially any manner
including randomly, static assignment via network planning or
configuration, historical based, and the like. According to one
example, for a given combination of .alpha..sub.1 and
.alpha..sub.2, the message, M, can be mapped to
M=210*.alpha..sub.1+.alpha..sub.2, for example. Because
p.sub.i.sup.210=1, for i=1, 2, the code of the aforementioned
equation can be periodic with a period of 210/21=10 symbols; thus,
X(.alpha..sub.1, .alpha..sub.2)=X.sub.t+10(.alpha..sub.1,
.alpha..sub.2) for a given value of t, in one example. The beacon
symbols can be shifted according to subcarrier in this way to
convey information to a receiver, for example.
According to yet another example for transmitting a beacon code, 47
subcarriers can be used to facilitate communicating between base
stations 502 and devices within range of one or more sectors. In
this regard, subcarriers 0-46 can be utilized to send beacon
symbols (as well as other data); as in the previous example, a
12-bit beacon code, for example, can require support of 4096
different sequences. To facilitate such, the beacon symbol can be
transmitted on a subcarrier with index X.sub.t(.alpha..sub.1,
.alpha..sub.2, .alpha..sub.3), which can be expressed as:
X.sub.t(.alpha..sub.1,.alpha..sub.2,.alpha..sub.3)=p.sub.1.sup..alpha..su-
p.1.sup.+2t.sym.p.sub.2.sup..alpha..sup.2.sup.+.alpha..sup.1.sup.+2t.sym.p-
.sub.3.sup..alpha..sup.3.sup.+.alpha..sup.1.sup.+2t, where p.sub.1
and p.sub.2 can be primitive elements of field Z.sub.47 (which can
comprise 47 elements representing the subcarriers), .alpha..sub.1,
.alpha..sub.2, and .alpha..sub.3 can be exponent factors determined
based at least in part on the beacon message (as described infra),
and .sym. denotes modulo addition. In this example, the exponent
factors .alpha..sub.1, .alpha..sub.2, and .alpha..sub.3 can be
defined as: 0.ltoreq..alpha..sub.1<2,
0.ltoreq..alpha..sub.2<46, and 0.ltoreq..alpha..sub.3<46.
Thus, a total of 2*46*46=4232 disparate combinations of
.alpha..sub.1, .alpha..sub.2, and .alpha..sub.3 can be defined by
the equation, thus, supporting the required 4096 combinations for
the beacon symbol. The beacon message can be mapped to a
combination in one example as
M=2116*.alpha..sub.1+46*.alpha..sub.2+.alpha..sub.3. Additional
and/or alternative mappings can be used as well as described supra.
Because p.sub.i.sup.46=1, for i=1, 2, 3, the code can be periodic
with a period of 46/2=23 symbols, for example; thus,
X.sub.t(.alpha..sub.1, .alpha..sub.2,
.alpha..sub.3)=X.sub.t+23(.alpha..sub.1, .alpha..sub.2,
.alpha..sub.3) for a given t.
Another example using an MDS code, which will be referred to
hereinafter as "beacon code B'," can be a Reed-Solomon code
designed using 47 subcarriers to transmit beacon symbols (e.g. n=47
in the subcarriers for symbol period 402). As in the previous
example, a 12-bit beacon code, for example, can require support of
4096 different sequences. To facilitate such, the beacon symbol can
be transmitted on a subcarrier with index X.sub.t(.alpha..sub.1,
.alpha..sub.2, .alpha..sub.3), which can be expressed as:
X.sub.t(.alpha..sub.1,.alpha..sub.2,.alpha..sub.3)=p.sub.1.sup..alpha..su-
p.1.sup.+2t.sym.p.sub.1.sup..alpha..sup.2p.sub.2.sup.2t.sym.p.sub.1.sup..a-
lpha..sup.3p.sub.3.sup.2t, where p.sub.1 can be a primitive element
of field Z.sub.47 (which can comprise 47 elements representing the
subcarriers), p.sub.2=p.sub.1.sup.2, p.sub.3=p.sub.1.sup.3, and
.alpha..sub.1, .alpha..sub.2, and .alpha..sub.3 can be exponent
factors determined based at least in part on the beacon message (as
described herein). In this example, arithmetic operations can be
over the field Z.sub.47, and in one example, p.sub.1=45,
p.sub.2=p.sub.1.sup.2=4, and p.sub.3=p.sub.1.sup.3=39; other
primitive elements can be used for p.sub.1 as well. The selection
p.sub.2=p.sub.1.sup.2 and p.sub.3=p.sub.1.sup.3 results in a
Reed-Solomon code in the above equation, for example. Additionally,
.alpha..sub.1, .alpha..sub.2, and .alpha..sub.3 can be defined as:
0.ltoreq..alpha..sub.1<2, 0.ltoreq..alpha..sub.2<46, and
0.ltoreq..alpha..sub.3<46. More than 4096 disparate combinations
of .alpha..sub.1, .alpha..sub.2, and .alpha..sub.3 can be defined
by the equation. Because p.sub.i.sup.46=1, for i=1, 2, 3, the code
can be periodic with a period of 46/2=23 symbols, for example;
thus, X.sub.t(.alpha..sub.1, .alpha..sub.2,
.alpha..sub.3)=X.sub.t+23(.alpha..sub.1, .alpha..sub.2,
.alpha..sub.3) for a given t.
It is to be appreciated that the subject matter as described herein
is not so limited to the foregoing examples presented. Rather, the
examples are two of substantially any number of implementations and
are presented herein to facilitate discussion. Other schemes can be
utilized as well, such as for example a purged MDS code designed
such that a terminal or device can decode a beacon based only on
one beacon symbol. It is to be appreciated that beacon codes can be
selected according to many factors, such as those mentioned herein
including network planning, derived information regarding other
sectors or beacons, as well as, based on beacon message length,
number of available carriers, desired performance (e.g.
signal-to-noise ratio).
Referring to FIGS. 6-7, methodologies relating to broadcasting
beacons or symbols thereof on a plurality of subcarriers and symbol
periods are illustrated. While, for purposes of simplicity of
explanation, the methodologies are shown and described as a series
of acts, it is to be understood and appreciated that the
methodologies are not limited by the order of acts, as some acts
may, in accordance with one or more embodiments, occur in different
orders and/or concurrently with other acts from that shown and
described herein. For example, those skilled in the art will
understand and appreciate that a methodology could alternatively be
represented as a series of interrelated states or events, such as
in a state diagram. Moreover, not all illustrated acts may be
required to implement a methodology in accordance with one or more
embodiments.
Turning to FIG. 6, illustrated is a methodology 600 that
facilitates transmitting multiple beacon symbols on disparate
symbol periods or time slots using the same or different
subcarriers to facilitate avoiding beacon symbol collision between
sectors. At 602, a first symbol period and subcarrier are selected
for transmitting a first beacon symbol. It is to be appreciated
that the beacon symbol can comprise information regarding the
sender of the symbol, such as an identifier or other communication
data. The beacon symbol, in one example, can be transmitted
utilizing substantially all available power for the subcarrier at
the given symbol period. To avoid collision, a second symbol period
and subcarrier can be selected for transmitting a second beacon
symbol at 604. The subcarrier can be the same as utilized for the
first beacon symbol or a different subcarrier in available
bandwidth. It is to be appreciated that the same or different
transmitters can be utilized to send the beacon symbols; the scheme
of selecting different times at which to send the symbols can avoid
collisions of the beacon symbols with respect to a receiving
device, for example. The symbol periods and/or subcarriers can be
selected according to many different schemes, such as those
described previously, including but not limited to network
planning, information obtained regarding other transmitters
(whether from the transmitter or devices roaming about), inferences
made from other acquired information about transmitters, such as a
manufacturer and/or bandwidth used, etc.
At 606, the first beacon symbol can be sent during the first time
slot or symbol period and on the first subcarrier. For example,
this can be a symbol period of a superframe in an OFDM
configuration; the beacon symbol can be substantially the only
transmission occurring during the symbol period in one example. At
608, the second beacon symbol is sent during the second symbol
period on the subcarrier. The second symbol period can be in the
same or a different superframe, for example; also, the second
subcarrier can be the same or different than the first subcarrier.
In one example, the first and second beacon symbols can be
transmitted from different areas; however, the beacon symbols can
also be part of a beacon code or pattern transmitted for one area.
Accordingly, the beacon can be decoded in its entirety by decoding
the separate beacon symbols in one example. Moreover, according to
one example, the beacon symbols can be sent according to a timer in
a synchronous communications environment.
Now referring to FIG. 7, a methodology 700 that facilitates
receiving a plurality of beacon symbols of different symbol periods
and subcarriers is illustrated. At 702, a first beacon symbol is
received during a first symbol period. This can be a symbol period
of a given superframe in an OFDM wireless communication network,
for example, and can be received on a single, or a small number of,
subcarrier(s) in the bandwidth. The subcarriers can transmit
symbols to facilitate communication. In one example, the beacon
symbol can be particularly strong as it can be the only symbol
transmitted in a given period from a transmitter. Though the
receiving entity can receive other symbols from other transmitters,
in one embodiment, the beacon symbol can be easily identified as it
can be the only symbol used in the carrier. At 704, a second beacon
symbol is received in a second symbol period. It is to be
appreciated that this symbol can be transmitted on the same or a
different subcarrier; additionally, the beacon symbol can be sent
by the same or a different carrier or sector, for example.
At 706, a first set of beacon symbols can be decoded to determine
information about the transmitter of the symbol. As described, this
information can include an identifier for the transmitter and/or
communication specifications; the information can also or
alternatively include specifications regarding other beacon
symbols, where the beacon can be comprised of one or more patterns
of symbols. At 708, a second set of second beacon symbols can be
decoded to determine information about the transmitter. It is to be
appreciated that the transmitter of the first and second symbols
sets can be different or the same transmitters. In this regard,
additional information can be comprised within the second beacon
symbol, which can relate to the transmitter and/or regarding other
beacon symbols from the transmitter, for example. Moreover, the
steps 706 and 708, or substantially any of the steps shown can
execute in serial or in parallel.
It will be appreciated that, in accordance with one or more aspects
described herein, inferences can be made regarding selecting or
determining a symbol period and/or subcarrier on which to send one
or more beacon symbols as described. As used herein, the term to
"infer" or "inference" refers generally to the process of reasoning
about or inferring states of the system, environment, and/or user
from a set of observations as captured via events and/or data.
Inference can be employed to identify a specific context or action,
or can generate a probability distribution over states, for
example. The inference can be probabilistic--that is, the
computation of a probability distribution over states of interest
based on a consideration of data and events. Inference can also
refer to techniques employed for composing higher-level events from
a set of events and/or data. Such inference results in the
construction of new events or actions from a set of observed events
and/or stored event data, whether or not the events are correlated
in close temporal proximity, and whether the events and data come
from one or several event and data sources.
According to an example, one or more methods presented above can
include making inferences pertaining to selecting one or more
symbol periods or subcarriers for transmitting beacon symbols. By
way of further illustration, an inference can be made with regard
to information gathered about other entities transmitting beacon
symbols (where acquired by the inferring entity or other entities
moving about the transmission area). It will be appreciated that
the foregoing examples are illustrative in nature and are not
intended to limit the number of inferences that can be made or the
manner in which such inferences are made in conjunction with the
various embodiments and/or methods described herein.
FIG. 8 is an illustration of a mobile device 800 that facilitates
receiving beacon symbols in a plurality of time slots and/or on a
plurality of subcarriers (e.g. for a superframe in an OFDM
communication network). Mobile device 800 comprises a receiver 802
that receives a signal from, for instance, a receive antenna (not
shown), and performs typical actions thereon (e.g., filters,
amplifies, downconverts, etc.) the received signal and digitizes
the conditioned signal to obtain samples. Receiver 802 can be, for
example, an MMSE receiver, and can comprise a demodulator 804 that
can demodulate received symbols and provide them to a processor 806
for channel estimation. Processor 806 can be a processor dedicated
to analyzing information received by receiver 802 and/or generating
information for transmission by a transmitter 816, a processor that
controls one or more components of mobile device 800, and/or a
processor that both analyzes information received by receiver 802,
generates information for transmission by transmitter 816, and
controls one or more components of mobile device 800.
Mobile device 800 can additionally comprise memory 808 that is
operatively coupled to processor 806 and that can store data to be
transmitted, received data, information related to available
channels, data associated with analyzed signal and/or interference
strength, information related to an assigned channel, power, rate,
or the like, and any other suitable information for estimating a
channel and communicating via the channel. Memory 808 can
additionally store protocols and/or algorithms associated with
estimating and/or utilizing a channel (e.g., performance based,
capacity based, etc.).
It will be appreciated that the data store (e.g., memory 808)
described herein can be either volatile memory or nonvolatile
memory, or can include both volatile and nonvolatile memory. By way
of illustration, and not limitation, nonvolatile memory can include
read only memory (ROM), programmable ROM (PROM), electrically
programmable ROM (EPROM), electrically erasable PROM (EEPROM), or
flash memory. Volatile memory can include random access memory
(RAM), which acts as external cache memory. By way of illustration
and not limitation, RAM is available in many forms such as
synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM
(SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM
(ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM).
The memory 808 of the subject systems and methods is intended to
comprise, without being limited to, these and any other suitable
types of memory.
Receiver 802 is further operatively coupled to a timer 810 that can
facilitate communicating in a synchronous communication
configuration such that timing can be a factor in evaluating
transmissions received by the receiver 802, for example. According
to an example, a transmission can be classified based in part on
the time slot or symbol period on which it is sent (e.g. a beacon
symbol as described herein). Additionally, a beacon symbol decoder
812 can utilize the timer 810 to determine if a received symbol is
a beacon symbol, whether a single symbol or part of a code or
pattern. According to one example, the beacon symbol decoder 812
can identify a beacon symbol following demodulation by the demod
804 as well. Accordingly, the receiver 802 can receive one or more
beacon symbols on a plurality of subcarriers across a plurality of
symbol periods and leverage the beacon symbol decoder 812 to gather
information from the beacon symbol (such as a sector identifier, a
period for the beacon, the number of symbols in a beacon code, and
substantially any information regarding the beacon symbol or the
transmitter thereof), for example. Because the beacon symbol
decoder 812 can decode beacon symbols received regardless of the
time slot received in, transmitters can broadcast beacon symbols in
a plurality of time slots to avoid collision therebetween. To this
end, the timer 810 can also help interpret the beacon symbols and
determine when other symbols can be expected, for example. Mobile
device 800 still further comprises a modulator 814 and a
transmitter 816 that can transmits a communication signal to, for
instance, a base station, another mobile device, etc. As described
previously, in one example, the mobile device 800 can receive and
provide beacon symbol information from one or more beacon symbol
transmitters to one or more other beacon symbol transmitters to
facilitate effective beacon symbol time shifting as described
supra. Although depicted as being separate from the processor 806,
it is to be appreciated that timer 810, beacon symbol decoder 812
and/or modulator 814 can be part of processor 806 or a number of
processors (not shown).
FIG. 9 is an illustration of a system 900 that facilitates
transmitting one or more beacon symbols in different time slots or
symbol periods and/or different subcarriers thereof. For example,
the system 900 can operate in an OFDM communication network where
beacon symbols can be sent in different symbol periods of a
superframe using one or substantially one subcarrier. The system
900 comprises a base station 902 (e.g., access point, . . . ) with
a receiver 910 that receives signal(s) from one or more mobile
devices 904 (and a demod 912 that can demodulate such signals)
through a plurality of receive antennas 906, and a transmitter 924
that transmits to the one or more mobile devices 904 through a
transmit antenna 908. The transmitter 924 can transmit one or more
beacon symbols related to the base station 902, for example. The
beacon symbol can identify information regarding the base station
902 and/or one or more sectors thereof. For example, the beacon
symbol can serve to identify the base station 902 and/or sector;
additionally, the beacon symbol can be part of an overriding beacon
that spans a plurality of beacon symbols in one example. The beacon
symbol can be modulated to a frequency domain by the modulator 922
and transmitted by one or more transmitter antennas 908 using the
transmitter 924, for instance.
For example, the base station can leverage a beacon symbol assignor
920, as described herein, to select (and/or determine, such as
based on inference as described supra) one or more symbol periods
and/or subcarriers for transmitting a beacon symbol. In so doing,
the base station 902 can participate in a network having many
transmitting sectors in range of a device at a given time with only
a limited number of bandwidth; by allowing the beacon symbols to be
transmitted on different symbol periods in a superframe thus
increasing the number of possible beacon symbol transmission slots
exponentially to the number of subcarriers. In one example, the
timer 918 can help facilitate this functionality by allowing the
base station 902 to send out the beacon symbols in the selected
time period in a synchronous communication network. It is to be
appreciated that the timer 918 and beacon symbol assignor 920 can
be leveraged by the processor 914 to effectuate this functionality.
Additionally or alternatively, some or all of the timer 918 and
beacon symbol assignor 920 can reside in, or be implemented by, the
processor 914. Furthermore, the memory 916 can comprise
instructions to facilitate the foregoing functionality. Moreover,
the memory 916 can comprise information regarding the symbol
periods and/or subcarriers to use in transmitting the beacon
symbols as well. As described, this can be derived from various
sources, such as network planning, other devices, inferred from
behavior or information of past uses or other devices, for
example.
FIG. 10 shows an example wireless communication system 1000. The
wireless communication system 1000 depicts one base station 1010
and one mobile device 1050 for sake of brevity. However, it is to
be appreciated that system 1000 can include more than one base
station and/or more than one mobile device, wherein additional base
stations and/or mobile devices can be substantially similar or
different from example base station 1010 and mobile device 1050
described below. In addition, it is to be appreciated that base
station 1010 and/or mobile device 1050 can employ the systems
(FIGS. 1-3 and 8-9), techniques/configurations (FIGS. 4-5) and/or
methods (FIGS. 6-7) described herein to facilitate wireless
communication there between.
At base station 1010, traffic data for a number of data streams is
provided from a data source 1012 to a transmit (TX) data processor
1014. According to an example, each data stream can be transmitted
over a respective antenna. TX data processor 1014 formats, codes,
and interleaves the traffic data stream based on a particular
coding scheme selected for that data stream to provide coded
data.
The coded data for each data stream can be multiplexed with pilot
data using orthogonal frequency division multiplexing (OFDM)
techniques. Additionally or alternatively, the pilot symbols can be
frequency division multiplexed (FDM), time division multiplexed
(TDM), or code division multiplexed (CDM). The pilot data is
typically a known data pattern that is processed in a known manner
and can be used at mobile device 1050 to estimate channel response.
The multiplexed pilot and coded data for each data stream can be
modulated (e.g., symbol mapped) based on a particular modulation
scheme (e.g., binary phase-shift keying (BPSK), quadrature
phase-shift keying (QPSK), M-phase-shift keying (M-PSK),
M-quadrature amplitude modulation (M-QAM), etc.) selected for that
data stream to provide modulation symbols. The data rate, coding,
and modulation for each data stream can be determined by
instructions performed or provided by processor 1030.
The modulation symbols for the data streams can be provided to a TX
MIMO processor 1020, which can further process the modulation
symbols (e.g., for OFDM). TX MIMO processor 1020 then provides
N.sub.T modulation symbol streams to N.sub.T transmitters (TMTR)
1022a through 1022t. In various embodiments, TX MIMO processor 1020
applies beamforming weights to the symbols of the data streams and
to the antenna from which the symbol is being transmitted.
Each transmitter 1022 receives and processes a respective symbol
stream to provide one or more analog signals, and further
conditions (e.g., amplifies, filters, and upconverts) the analog
signals to provide a modulated signal suitable for transmission
over the MIMO channel. Further, N.sub.T modulated signals from
transmitters 1022a through 1022t are transmitted from N.sub.T
antennas 1024a through 1024t, respectively.
At mobile device 1050, the transmitted modulated signals are
received by NR antennas 1052a through 1052r and the received signal
from each antenna 1052 is provided to a respective receiver (RCVR)
1054a through 1054r. Each receiver 1054 conditions (e.g., filters,
amplifies, and downconverts) a respective signal, digitizes the
conditioned signal to provide samples, and further processes the
samples to provide a corresponding "received" symbol stream.
An RX data processor 1060 can receive and process the N.sub.R
received symbol streams from N.sub.R receivers 1054 based on a
particular receiver processing technique to provide N.sub.T
"detected" symbol streams. RX data processor 1060 can demodulate,
deinterleave, and decode each detected symbol stream to recover the
traffic data for the data stream. The processing by RX data
processor 1060 is complementary to that performed by TX MIMO
processor 1020 and TX data processor 1014 at base station 1010.
A processor 1070 can periodically determine which precoding matrix
to utilize as discussed above. Further, processor 1070 can
formulate a reverse link message comprising a matrix index portion
and a rank value portion.
The reverse link message can comprise various types of information
regarding the communication link and/or the received data stream.
The reverse link message can be processed by a TX data processor
1038, which also receives traffic data for a number of data streams
from a data source 1036, modulated by a modulator 1080, conditioned
by transmitters 1054a through 1054r, and transmitted back to base
station 1010.
At base station 1010, the modulated signals from mobile device 1050
are received by antennas 1024, conditioned by receivers 1022,
demodulated by a demodulator 1040, and processed by a RX data
processor 1042 to extract the reverse link message transmitted by
mobile device 1050. Further, processor 1030 can process the
extracted message to determine which precoding matrix to use for
determining the beamforming weights.
Processors 1030 and 1070 can direct (e.g., control, coordinate,
manage, etc.) operation at base station 1010 and mobile device
1050, respectively. Respective processors 1030 and 1070 can be
associated with memory 1032 and 1072 that store program codes and
data. Processors 1030 and 1070 can also perform computations to
derive frequency and impulse response estimates for the uplink and
downlink, respectively.
It is to be understood that the embodiments described herein can be
implemented in hardware, software, firmware, middleware, microcode,
or any combination thereof. For a hardware implementation, the
processing units can be implemented within one or more application
specific integrated circuits (ASICs), digital signal processors
(DSPs), digital signal processing devices (DSPDs), programmable
logic devices (PLDs), field programmable gate arrays (FPGAs),
processors, controllers, micro-controllers, microprocessors, other
electronic units designed to perform the functions described
herein, or a combination thereof.
When the embodiments are implemented in software, firmware,
middleware or microcode, program code or code segments, they can be
stored in a machine-readable medium, such as a storage component. A
code segment can represent a procedure, a function, a subprogram, a
program, a routine, a subroutine, a module, a software package, a
class, or any combination of instructions, data structures, or
program statements. A code segment can be coupled to another code
segment or a hardware circuit by passing and/or receiving
information, data, arguments, parameters, or memory contents.
Information, arguments, parameters, data, etc. can be passed,
forwarded, or transmitted using any suitable means including memory
sharing, message passing, token passing, network transmission,
etc.
For a software implementation, the techniques described herein can
be implemented with modules (e.g., procedures, functions, and so
on) that perform the functions described herein. The software codes
can be stored in memory units and executed by processors. The
memory unit can be implemented within the processor or external to
the processor, in which case it can be communicatively coupled to
the processor via various means as is known in the art.
With reference to FIG. 11, illustrated is a system 1100 that
broadcasts beacon symbols in different symbol periods of a
synchronous wireless communication system. For example, system 1100
can reside at least partially within a base station It is to be
appreciated that system 1100 is represented as including functional
blocks, which can be functional blocks that represent functions
implemented by a processor, software, or combination thereof (e.g.,
firmware). System 1100 includes a logical grouping 1102 of
electrical components that can act in conjunction. For instance,
logical grouping 1102 can include an electrical component for
dividing a superframe (e.g. in an OFDM communications
configuration) into one or more symbol periods 1104. For example,
the symbol periods can be utilized to add a time factor to wireless
communications; accordingly, devices can be synchronized using the
time for purposes such as identifying data sent and/or a source
thereof, for example. Further, logical grouping 1102 can comprise
an electrical component for synchronously communicating within the
symbol periods 1106. As described supra, this can be a timer or
another type of clock that can allow devices in the network to send
and receive data according to time, for example. Moreover, logical
grouping 1102 can include an electrical component for selecting one
of the symbol periods for transmitting a beacon symbol to avoid
collision with a second beacon symbol of another sector 1108.
According to an example, the system 1100 can receive information
related to a symbol period to utilize in sending a beacon symbol to
mitigate collisions with other sectors; as described previously,
this information can come from network planning, received from
other devices, discerned by the system 1100 based on other received
information, and the like. Furthermore, logical grouping 1102 can
comprise an electrical component for transmitting the beacon symbol
in the selected period 1110. In this regard, collisions can be
avoided as shown. Additionally, system 1100 can include a memory
1112 that retains instructions for executing functions associated
with electrical components 1104, 1106, 1108, and 1110. While shown
as being external to memory 1112, it is to be understood that one
or more of electrical components 1104, 1106, 1108, and 1110 can
exist within memory 1112.
Turning to FIG. 12, illustrated is a system 1200 that receives a
plurality of beacon symbols transmitted in different time periods.
System 1200 can reside within a mobile device, for instance. As
depicted, system 1200 includes functional blocks that can represent
functions implemented by a processor, software, or combination
thereof (e.g., firmware). System 1200 includes a logical grouping
1202 of electrical components that facilitate receiving and
decoding the beacon symbols. Logical grouping 1202 can include an
electrical component for synchronously communicating in a wireless
communications network 1204. For example, as described with
reference to the previous figure, the system 1200 can operate in a
synchronous communication configuration where transmissions can
occur in different discernable time periods. This information can
be used to develop further information with regard to transmission.
Moreover, logical grouping 1202 can include an electrical component
for receiving a first beacon symbol in a first symbol time period
in a superframe 1206. As available bandwidth can be broken up by
time, the symbol periods can be used to transmit information; the
beacon symbol can be sent on one or more available symbol periods
in the superframe. It is to be appreciated that some of the other
symbol periods can be used to transmit other data, such as
communication data. Further, logical grouping 1202 can comprise an
electrical component for receiving a second beacon symbol in a
second symbol period of the superframe 1208. In this regard,
multiple symbol periods of a superframe can be used for
transmitting beacon symbols, thus mitigating collisions between
transmitting sectors. Also, logical grouping 1202 can include an
electrical component for decoding the first and second beacon
symbols to identify the sectors transmitting the beacon symbols
1210. For example, the beacon symbols can comprise information
regarding the sectors such as identification and/or preferred
carrier information. Also, a beacon symbol can be part of an entire
beacon pattern that comprises such information in one example.
Additionally, system 1200 can include a memory 1212 that retains
instructions for executing functions associated with electrical
components 1204, 1206, 1208, and 1210. While shown as being
external to memory 1212, it is to be understood that electrical
components 1204, 1206, 1208, and 1210 can exist within memory
1212.
What has been described above includes examples of one or more
embodiments. It is, of course, not possible to describe every
conceivable combination of components or methodologies for purposes
of describing the aforementioned embodiments, but one of ordinary
skill in the art may recognize that many further combinations and
permutations of various embodiments are possible. Accordingly, the
described embodiments are intended to embrace all such alterations,
modifications and variations that fall within the spirit and scope
of the appended claims. Furthermore, to the extent that the term
"includes" is used in either the detailed description or the
claims, such term is intended to be inclusive in a manner similar
to the term "comprising" as "comprising" is interpreted when
employed as a transitional word in a claim.
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